The present invention relates to a turbine for use in refrigeration cycle, particularly capable of increasing turbine output without reducing the capacity of refrigeration cycle.
Turbines for use in refrigeration cycle have become popular. Refrigerating medium compressed by the compressor is fed to the condenser in the course of usual refrigeration cycle. The refrigerating medium is liquidized here, introduced through the capillary tube or expansion valve into the evaporator, and fed to the compressor after having passed through the evaporator. The refrigerating medium passed through the capillary tube or expansion valve in this refrigeration cycle is caused to have large kinetic energy because energy charged due to high pressure is released. Paying attention to the fact that the refrigerating medium has such kinetic energy as described above, a system has been realized in which a turbine is driven by said refrigerating medium of large kinetic energy and turbine output thus obtained is used to reduce total power consumption. The turbine used to this end is connected between the capillary tube (or expansion valve) and the evaporator. The turbine has a turbine runner freely rotatable in a casing and this turbine is driven by said refrigerating medium of large kinetic energy.
The conventional turbine used as described above in a refrigeration cycle comprises a space formed inside the casing with its central axis directed horizontally, the turbine runner supported in the space with its rotary shaft directed horizontally, an inlet provided in the circumferential wall of said casing and through which the refrigerating medium to be blown to the turbine runner is introduced, and an outlet provided in the circumferential wall of said casing and through which the refrigerating medium is discharged. These conventional turbines, however, had some following points to be improved. The refrigerating medium for driving the turbine runner is usually blown to the turbine runner under gas-liquid-mixed state and separated due to the difference of specific gravity into the liquid part falling downward and the gas part rising upward. This refrigerating liquid is gathered on the bottom of said casing and becomes so high in level as to immerse the lower portion of said turbine runner. When the turbine runner is rotated with its lower portion immersed in the refrigerating liquid in the casing, power is needed to overcome the friction caused between the turbine runner and the refrigerating liquid. This power is a loss at the time of driving the turbine runner and turbine output is therefore reduced by this loss. When the refrigeration cycle is ceased, the refrigerating medium in the cycle forms a mass in each of low temperature portions and the refrigerating liquid collected on the bottom of said casing often becomes so high in level as to immerse the lower portion of the turbine runner as each section of said refrigeration cycle is cooled. When the refrigeration cycle is started under this state, large starting force is needed, the time during which the turbine runner is started and reaches its steady state revolution becomes long, during which the refrigerating medium is stirred by the turbine runner, making its flow unstable and therefore causing a loss in its flow, and input power necessary to drive the compressor must be increased. It is preferable that the refrigerating medium passing through the turbine changes under equal entropy state, but the refrigerating medium usually moves in a direction in which said entropy increases. Namely, the dryness fraction of refrigerating medium becomes high and gas irrelevant to refrigerating capacity increases. When the refrigerating medium of this state is fed to the evaporator, pressure loss is increased because of the presence of the gas in the evaporator and the efficiency of whole refrigeration cycle is reduced. When considering the whole of refrigeration cycle, therefore, power consumption necessary to operate said refrigeration cycle could not be sufficiently reduced even in view of mechanical power obtained from the turbine.
Above described problem is occurred when the turbine is connected between the condenser and the capillary tube, or when the capillary tube is formed with a series connected two tubes and the turbine is provided between the two capillary tubes.